1. Field of the Invention
This invention resides in the field of process equipment used in the treatment of materials in liquid media by ultrasound.
2. Description of the Prior Art
The use of ultrasound for driving chemical reactions is well known. Examples of publications that describe chemical uses of ultrasound are Suslick, K. S., Science, vol. 247, p. 1439 (1990), and Mason, T. J., Practical Sonochemistry, A User's Guide to Applications in Chemistry and Chemical Engineering, Ellis Norwood Publishers, West Sussex, England (1991). Of the various sonicating systems that have been developed, those known as “probe”-type systems include an ultrasonic transducer that generates ultrasonic energy and transmits that energy to an ultrasonic horn for amplification.
Ultrasound generators are generally of limited energy output due to the power needed to drive the vibrations and the heat generated by ultrasonic transducers. Because of these limitations, the use of ultrasound for large-scale chemical processes has met with limited success. One means of achieving ultrasonic vibrations at a relatively high power is by the use of magnetostriction-driven ultrasound transducers, but frequencies attainable by magnetostriction drives are still only moderate in magnitude. Disclosures of the magnetostriction ultrasound transducers and their use in chemical reactions appear in Ruhman, A. A., et al. U.S. Pat. No. 6,545,060 B1 (issued Apr. 8, 2003), and its PCT counterpart WO 98/22277 (published May 28, 1998), as well as Yamazaki, N., et al. U.S. Pat. No. 5,486,733 (issued Jan. 23, 1996), Kuhn, M. C., et al. U.S. Pat. No. 4,556,467 (issued Dec. 3, 1985), Blomqvist, P., et al. U.S. Pat. No. 5,360,498 (issued Nov. 1, 1994), and Sawyer, H. T., U.S. Pat. No. 4,168,295 (issued Sep. 18, 1979). The Ruhman et al. patent discloses a magnetostriction transducer that produces ultrasonic vibrations in a continuous-flow reactor in which the vibrations are oriented radially relative to the direction of flow and the frequency range is limited to a maximum of 30 kHz. The Yamazaki et al. patent discloses a small-scale ultrasonic horn operating at relatively low power, in which magnetostriction is listed as one of a group of possible vibration-generating sources together with piezoelectric elements and electrostrictive strain elements. The Kuhn et al. patent discloses a continuous-flow processor that includes a multitude of ultrasonic horns and generators supplying frequencies less than 100 kHz. The Blomqvist et al. patent discloses an ultrasonic generator utilizing a magnetostrictive powder composite operating at a resonance frequency of 23.5 kHz. The Sawyer et al. patent discloses a flow-through reaction tube with three sets of ultrasonic transducers, each set containing four transducers and delivers ultrasound at a frequency of 20 to 40 kHz. These systems are suitable for high-throughput reactions where a high reaction yield is required.